Catalysts are important components of many chemical manufacturing processes, and may typically be used to accelerate the rate of the reaction in question and/or to increase the selectivity or efficiency towards the desired product(s). Utilized in connection with many reactions, catalysts find particularly advantageous use in the epoxidation of olefins, a process of significant commercial importance in the commodity chemical business. In epoxidation reactions, a feed containing at least the olefin and oxygen is contacted with a catalyst causing the formation of the corresponding olefin oxide.
One example of an olefin epoxidation of particular commercial importance is the epoxidation of alkylenes, or mixtures of alkylenes, and this epoxidation reaction in particular can rely upon high performing catalysts in order to be commercially viable. Those of skill in the art have actively sought improvements in the efficiency and/or activity of epoxidation catalysts for some time, since, on a commercial scale, even slight, e.g., 1%, increases in selectivity can substantially reduce the operating costs associated with the epoxidation processes.
One method thought to be capable of improving catalyst performance is the impregnation thereupon of an optimized amount of a catalytic species. The amount of such catalytic species capable of being deposited onto a carrier, in turn, is thought to be related to one or more of surface area, pore size distribution, water absorption, and total pore volume of the catalyst support. And so, many efforts have focused on providing a support having a combination of these properties that not only provides a sufficiently robust support to be commercially useful, but that also may readily be impregnated with the desired amount of catalytic species.
Very little attention has been paid to the particular conditions of the impregnation, and the impact of the same on the amount of catalytic species ultimately deposited, although it is generally thought that conducting the impregnations under conditions of a fairly high vacuum is required. More particularly, high vacuum levels, i.e., vacuum levels having low minimum residual pressures, e.g., of no more than 1-2 inches mercury, absolute (34-68 mbar), are recognized in the art as being required in order to remove trapped air from the pores of the support and to thus assist in the permeation of the catalytic species, or a precursor thereof, therein.
However, the use of excessive vacuum levels can add undesirable equipment cost, as well as time, to a catalyst production process. It would be beneficial to provide a method of providing such catalysts that can utilize supports having the desired characteristics, achieve the desired level of catalytic species loading, while yet, utilizing fewer resources.